Currently, the manufacture of nuclear fuels (actinide compounds) is typically performed via standard processes based on the metallurgy of powders. Two major steps are exploited to do so:                the forming of the constituent powders of the fuel (pressing with a potential prior preparation of the powders);        the sintering of the compact obtained after the powder pressing step.        
This type of process is proven and industrial, but induces at least four types of drawbacks:                the difficulty in controlling the shape of the components obtained from the sintering, which is itself conditioned by the control of the granular stack in the pressing molds (linked to the homogeneity of distribution of the material). Now, since actinide powders are, for some of them, relatively cohesive, this control is not trivial and usually requires preparation of the powders prior to their forming. For certain uses, the geometrical specifications impose rectification of the combustible objects obtained by metallurgy of the powders;        this preparation of the powders often induces powder dissemination, which leads to an increase in retention in the confinement chambers of the manufacturing process. The result of this is an increased radiological risk;        the impossibility of obtaining components/fuels whose shape is complex (i.e. any shape) and/or not axisymmetric since the forming is performed industrially by uniaxial pressing;        the need to render the confinement chambers containing the actinide powders inert so as to limit the risks of pyrophoricity (when the actinides are in metallic or carbide form notably).        
To act on all of these drawbacks, the Applicant proposes filled compositions that make it possible to use a process known as powder injection molding (PIM).
However, in order for this type of process to be operative for the use of actinide powders, it is necessary to have available an organic matrix consisting of organic components, generally based on polymers that allow good (in the sense of homogeneous distribution) incorporation of the powder into said organic matrix. This organic matrix must satisfy all of the objective functions and constraints imposed by this type of process in the light of the specificities of the nuclear materials to be used and of the specifications of the targeted fuels.
At the present time, no formulation of organic matrix for preparing actinide components is mentioned in the technical and scientific literature. This may notably be explained by the number of constraints/criteria weighing on a filled organic matrix. These are to be taken into account for the use of actinide powders which have specific properties, and under satisfactory conditions (i.e. conditions making it possible to obtain components whose characteristics are at least equivalent to those obtained by powder metallurgy).
Thus, to satisfy this general problem of manufacturing actinide fuels/components via the PIM process in a satisfactory manner, it is necessary for the envisioned filled matrix to concomitantly satisfy the following criteria:                an actinide powder filler content in the filled matrix that is sufficient to obtain after debinding granular stack densities of greater than 40%. (It is recalled that the debinding operation makes it possible to remove the constituent carbon-based compounds of the composite filler. This debinding may be performed conventionally via thermal action to volatilize the filler.)        
Specifically, when the PIM process is applied to actinide powders whose purpose is to result in objects whose characteristics are similar to those obtained by powder metallurgy, it is necessary after the step of debinding of the formed polymers to result in granular stacks that need to be cohesive, i.e. to keep their shape, and whose density is equivalent to that obtained by uniaxial powder pressing (powder metallurgy). A powder may be considered as cohesive if it notably satisfies the definition of Geldard (class C) or has a Hausner coefficient of greater than 1.4, “Techniques de l'ingenieur mise en forme des poudres, J 3 380-1”. To achieve this minimum filler content value, it is necessary for the powder, especially if it is cohesive, as is conventionally the case for actinide powders (and notably the oxides thereof), to be deagglomerated during the blending/preparation of the filler. This prerequisite is not trivial per se for the following reasons:                the injectability of the filler: despite the filler content criterion mentioned above, it is necessary to be able to use the filled matrix in a mold (or through a die if extrusion is performed), which imposes a shear viscosity range of between 50 and 10 000 Pa·s during injection with a preferential range of less than 1000 Pa·s for a rate gradient of 100 s−1;        the shear-thinning behavior and robustness of the rheological behavior with temperature, or more generally the blending conditions. The rheological behavior of the filler may prove to be prohibitive. Moreover, since actinide powders can be relatively dense, cohesive and polymodal, it is notably necessary to limit any risk of segregation/sedimentation in the filled matrix in the event of poor formulation or mixing condition during the blending;        the stability of the properties of the filled matrix, which means the following criteria:                    physicochemical compatibility, notably immiscibility of the polymers under the working conditions of the PIM process;            chemical stability (i.e. absence of notable chemical interaction between the polymers and between the polymers and the actinide powders used). Notably, this criterion demands that the mixture of the constituent polymers of the matrix be stable at least down to the lowest decomposition temperature of the constituents of the matrix of organic compounds.                        
Given that actinides are moreover compounds that are reputed to promote the decomposition of the constituent carbon-based compounds of the filled matrix (cf. “The activity and mechanism of uranium oxide catalysts for the oxidative destruction of volatile organic compounds”, S. H. Taylor, C. S. Heneghana, G. J. Hutchingsa et al., Catalysis Today, 59:249-259, 2000; A study of uranium oxide based catalysts for the oxidative destruction of short chain alkanes, Applied Catalysis B: environmental, 25:137-149, 2000, S. H. Taylor et al.), this stability criterion of the properties is not trivial to achieve with, notably, either a risk of modification of the degree of oxidation of the actinides in contact with the constituent compounds of the matrix, or a risk of formation of non-debindable carbon-based residues (which may thus be disadvantageous at the end of the manufacture depending on the residual content) during the implementation of the PIM process;                a debindable filled matrix without the need to use an aqueous solution and not containing any water. Specifically, the use of actinide powders induces an increased risk of criticality during the use of water and this use moreover induces a generation of liquid effluents that are always difficult to process in a nuclear environment.        
These acceptability criteria for the filled matrix are to be respected concomitantly given, moreover, the targeted actinide fuels/components must have characteristics at least equivalent to those that may be achieved by powder metallurgy, i.e., notably:                a density equivalent to at least 95% of the theoretical density of the target actinide compound after sintering of the components;        homogeneity of the microstructure, i.e. a uniform distribution of grain size and porosity;        control of the size, i.e. a variation of the dimensions of the fuel relative to the expected mean dimensions, i.e., for example and conventionally, a tolerance of ±12 microns for rectified REP pellets (8.19±0.012 mm);        a residual carbon mass content of less than 0.05% (for the cases of powders other than carbides).        